The proposed study is designed to investigate the chemical nature and biosynthesis of epidermal cell organelles observed morphologically under normal, experimental, and pathological conditions, in order to better understand biochemical changes involved in each stage of epidermal cell differentiation (the "keratinization" process). Autoradiographical, cytochemical, chemical and immunological techniques will be used. These results will clarify pathomechanisms of skin diseases associated with abnormal keratinization and contribute to the control of these diseases.